You won’t find it on the league calendar, but NFL free agency unofficially begins this week in Indianapolis.

It’s not even an open secret anymore. It’s just assumed.

Perhaps it’s a casual dinner at St. Elmo. Or a late-night cocktail at Prime 47. Or maybe just a passing conversation in the hallway at Lucas Oil Stadium.

But sometime, somehow, business that is technically supposed to be conducted next month will go down surreptitiously at the annual Scouting Combine, which brings all the league’s power brokers together in the frigid Midwest.

Premium content for only $0.99

Officially, the Combine is about evaluating the more than 300 college prospects in town with workouts, interviews and medical tests.

But that’s only half of the story. For the Dolphins, like the 31 other teams, it’s also about filling out their roster — with one eye on their own pending free agents and another on the veteran players who might become available in the next few weeks.

The Dolphins have more than a dozen unrestricted free agents, including significant contributors in Jared Odrick, Charles Clay, Louis Delmas and Jimmy Wilson. They presumably want to keep many of these players. But they have yet to make significant headway on any of them.

That probably will change this week. The belief in league circles is the Dolphins will dive headfirst into the process in Indianapolis. A potential agenda item would be beginning the arduous process of working out a long-term extension with Ryan Tannehill. The team wants to lock him up for the foreseeable future, but there is no rush; they own his rights through the 2016 season.

Tannehill has improved statistically each year of his career. But if more Dolphins players developed like he has, they wouldn’t have to hit free agency as hard as they are expected to again this spring.

Frankly, not enough of their own draft picks are contributing — either through lack of ability or lack of opportunity.

Since Joe Philbin became coach in 2012, the Dolphins have drafted 26 players. Ten of them started at least one game for the Dolphins last year, but just seven started more than three.

Compare that with the Super Bowl champion Patriots, who started 14 of their own draft picks, as well as Ryan Wendell, whom they signed as a rookie free agent, in Super Bowl 49.

A prevailing thought in league circles is that the Dolphins’ win-now attitude has stunted the growth of their players. Instead of relying on their young players to blossom, they have thrown big money at free agents — with mixed success. For every Branden Albert, there’s a Dannell Ellerbe and a Philip Wheeler.

An example: The team signed four established offensive linemen in free agency last year and still allowed 46 sacks, the 10th-most in football.

There are success stories. Lamar Miller and Olivier Vernon, teammates at the University of Miami and now with the Dolphins, have emerged as dependable starters. Jarvis Landry looks to be on his way to becoming a star.

Related stories from Miami Herald

The Dolphins’ problem is that they need more of those hits and fewer misses.

When asked to grade the team’s ability to develop its players, one league source said: “C to C-minus.”

Critics point to the team’s inability to adapt to its talent, both homegrown and imported. Mike Wallace was so unhappy last season in large part because the Dolphins didn’t play to his strengths.

And with a few notable exceptions — Tannehill and Ja’Wuan James being the most obvious — Philbin has not trusted his young draft picks, or known exactly how to use them.

Dion Jordan, the third pick in the 2013 draft, has started one game in his career — and it was in a role different from the one the team envisioned when it took him.

Corners Will Davis and Jamar Taylor, taken in the first three rounds in ’13, have played well in the few chances they have had, but defensive coordinator Kevin Coyle doesn’t appear convinced that they are the answer at the position moving forward. Most expect the team to sign a veteran to at least compete with them this fall.

Billy Turner, a third-round pick in 2014, was buried on the bench most of the season even though the team’s guard situation was a mess.

And the biggest surprise of the year — the emergence of linebacker Jelani Jenkins — might have only happened because Ellerbe was injured in the season opener.

The Dolphins are already feeling the pressure — they’re right up against the projected $140 million cap and will need to cut several veterans to go shop for new ones this spring — and it will only get worse after this year.

This is Tannehill’s final season as a bargain. His cap hit will go up significantly in 2016. Any more high-priced free agent misses could cripple this franchise.

Perhaps that’s why the Dolphins have been so quiet so far this offseason. They know they have to get it right.